The present invention relates to a fiber reinforced rubber article, particularly, the reinforcement embedded in a rubber article.
Since high plessley, high elasticity, high dimensional stability, and high adhesive strength has been required for rubber articles such as a belt, a tire, and a hose, a reinforcing cord constructed of fibers or of a reinforcing canvas is embedded in the rubber. Generally, a cord of twisted yarns is used for the reinforcement. The yarn may be all twisted, only half of them twisted, or lang lay. The yarns, all of them being twisted, are most popular for reinforcement for a rubber article.
However, the monofilaments in an all twisted yarn rub each other at a sharp angle in a rubber article, and the yarn is worn out, broken, or decreased plessley in the rubbed part after a short period of usage. Therefore, the flex fatigue of the cord is lowered.
Japanese Patent Application Laid Open Gazette No. 59-19744 proposed a fiber reinforced rubber article, in which the reinforcement is constructed of cords, half of the yarns being twisted, or lang lay, to solve the problem of lowered flex fatigue.
However, a rubber article reinforced by cords in which only half of the yarns are twisted or lang lay is lowered in elongation and rate of tensile elasticity after the dipping process, compared with a rubber article reinforced by cords in which all of the yarns are twisted. This results in lower dimensional stability.
On the other hand, a braided cord has been made for various purposes. A cylindrically braided cord which needs more than four yarns and an even number of yarns to make a cylindrical configuration, surpasses a twisted cord in flex fatigue and dimensional stability due to its constructional characteristics. Therefore, the cylindrically braided cord will improve both the flex fatigue resistance and dimensional stability if it is used as a reinforcement for a rubber article.
Moreover, in the case where the cylindrically braided cord is used for the reinforcement of a rubber article, if the yarns constructing the cord are twisted, the cord is arranged orderly and consequently, a higher strength of the a cylindrically braided and a longer service life of the rubber article is expected. On the other hand, if all the yarns, first twisted to the right and first twisted to the left, are twisted in the same direction, the cylindrically may possess a direction and a rubber article reinforced by such a cylindrically braided cord possessing a direction may not obtain a satisfactory result in flex fatigue resistance. For the above reason, yarns, first twisted to the right and first twisted to the left, need to be turned in the reverse direction of the first twist. However, even if such yarns, first twisted to the right and first twisted to the left, are turned in the reverse direction of the first twist, the ideal dynamic adhesive strength may not be obtained.